Reuse of hypodermic syringe products without sterilization or sufficient sterilization is believed to facilitate the transfer of contagious diseases.
A syringe which can be rendered inoperable after use presents a viable solution to these issues. Various syringes have been proposed and are commercially available that can be disabled by the user by taking active steps to disable the syringe. Single-use syringes that do not require the user to actively disable the syringe are also thought to offer a solution.
Prior art re-use prevention syringes containing frangible features position the frangible section near the stopper end or near the middle of the plunger rod. This positioning makes the plunger rod prone to the accidental breakage in bending due to the substantial lever distance from the frangible break section to the point of force application at the thumb press, which results in user dissatisfaction and adds to health care costs by wasting the device and the medication it contains. The prior art frangible section location may also make the plunger rod substantially flexible, requiring the clinician to change their conventional technique.
Several prior art re-use prevention syringes attempt to improve their lack of rigidity by making the frangible feature a plurality of break points. This adds manufacturing complexity by requiring intricate tooling (such as interlocking thin molding inserts) that is difficult to produce and maintain, which results in increased product cost, and by challenging the plastic to flow through multiple narrow channels of the frangible section, which may result in molding defects.
The prior art multiple frangible points solution leads to inconsistent axial break forces due to the cumulative effect of the manufacturing tolerances on each individual break feature. The present invention of the single frangible element adjacent to the thumb press requires that only one critical feature be dimensionally controlled to ensure consistent axial break forces, thus further improving the product performance over the prior art.
It would be desirable to provide syringes that are automatically or passively disabled from reuse and can be manufactured in a cost-effective manner by, for example, utilizing fewer or less complex parts. It is also desirable to provide a re-use prevention syringe wherein the frangible features are reinforced or positioned to reduce to possibility of accidental breakage.